The present invention relates in general to fluid filters and the selected design for connecting the filter to a mounting base or head. More specifically, the present invention relates to a spin-on filter that is constructed and arranged without using a nutplate for connecting the filter to a mounting base or head. By eliminating the nutplate, the resultant fluid filter is less expensive to fabricate, including cost savings by eliminating one of the component parts. A related benefit is the ability to have a mostly non-metallic construction for the fluid filter that in turn allows it to be considered “disposable” since it can be incinerated for disposal or recycling. By providing a construction that is incinerable, the structural mass of the filter can be reduced to low volume ash and this limits what will be added to landfills. The other option for “disposal” is to recycle the plastics used in the construction. Presently, when there is an all-plastic construction for a filter, it is generally described as having an “environmentally friendly green design”.
In one embodiment of the present invention, the focus is directed to a fluid filter construction that consists mostly or predominantly of non-metallic components and is considered to be disposable. This embodiment does not include the traditional nutplate for threaded connection to the head. Instead, the open end of the shell is externally threaded for connection to the head, enabling the elimination of the nutplate. In a related embodiment of the present invention, the filter housing or shell is a “hybrid” in that it includes both metal and plastic. This related embodiment also does not include the traditional nutplate for threaded connection to the head.
Typical spin-on fluid filters according to prior art designs are mounted to the head (spud) by the use of an internally-threaded metal nutplate. The nutplate is anchored to the fluid filter canister and includes at least one flow inlet and a flow exit cooperating with a centertube. The filter-to-head mounting includes a seal to prevent leakage between the head and the filter. Flow to the filter travels by way of the head and, once it is filtered, the fluid exits by way of the head. In order to fabricate a fluid filter using a nutplate, there are costs associated with the fabrication of the nutplate and costs associated with assembly of the nutplate into the fluid filter. If the nutplate could be eliminated from the fluid filter, these costs would be saved. While there may be, on a limited basis, other techniques used for connecting a fluid filter to a mounting head, one aspect of the present invention is directed to the elimination of any nutplate from the fluid filter. A consequence of this design is the elimination of the nutplate for use in connection to the head.
The present invention provides a fluid filter design that is capable of spin-on, threaded mounting to a head without using a nutplate. A typical prior art mounting head includes an externally-threaded post or portion that is received by the internally-threaded nutplate. With a non-nutplate construction, according to the present invention, the spin-on fluid filter attaches to the head by way of the externally threaded open end of the fluid filter shell. In the fluid filter construction disclosed by U.S. patent application Ser. No. 10/778,694, a threaded post is configured as part of the closed end of the canister and connects to a shaft (internally-threaded) that extends beyond the head into the spin-on filter. As described therein, there are various alternative embodiments. These embodiments include, among other features, fixing the shaft as part of the fluid filter and connecting the shaft to a cooperating portion of the head. It should also be understood that the use of “spin-on” to describe the fluid filter of the present invention is intended to include not only threaded engagement, but other connection techniques, such as the use of a bayonet connection between the fluid filter and the mounting head. Related to a bayonet connection are quarter-turn and half-turn connections that may assume a variety of structural forms.
With respect to the “hybrid” shell embodiment of the present invention, it is appropriate to discuss potential concerns with an all-plastic, unitary shell or housing. It is believed that an all-plastic construction, with threads on the outside diameter of the shell adjacent the open end, lends itself well to smaller diameters and shorter lengths, such as shells that are less than 7 inches tall. However, as fluid filters become larger in terms of the diameter and height, the unitary construction using all plastic can become technically and/or financially limiting. For example, additional amounts of plastic may be required in order to maintain the required strength for the higher stress levels. The injection molding tooling becomes more costly and the injection molding process requires a press design with larger tonnage. Using a hybrid shell with a metal body and a plastic sleeve for the threaded end of the metal body, according to the present invention, addresses some of these concerns.